The present invention also relates to field alignable pigments such as those that can be aligned or oriented in a magnetic or electric field, for example, flakes having an optically diffractive structure forming diffractive optically variable image devices (“DOVID”), such as orientable diffractive pigment flakes and stereograms, linegrams, graphic element-oriented devices, dot-oriented devices, and pixel-oriented devices, and oriented optically variable pigment flakes.
Optically variable pigments (“OVP's”™) are used in a wide variety of applications. They can be used in paint or ink, or mixed with plastic. Such paint or ink is used for decorative purposes or as an anti-counterfeiting measure on currency. One type of OVP uses a number of thin-film layers on a substrate that form an optical interference structure. Generally, a dielectric spacer layer is often formed on a reflector, and then a layer of optically absorbing material is formed on the spacer layer. Additional layers may be added for additional effects, such as adding additional spacer-absorber layer pairs. Alternatively optical stacks composed of (high-low-high)n or (low-high-low)n dielectric materials, or combinations of both, may be prepared.
U.S. Pat. No. 6,902,807 and U.S. Patent application publication numbers 2007/0058227, 2006/0263539, 2006/0097515, 2006/0081151, 2005/0106367, and 2004/0009309, disclose various embodiments related to the production and alignment of pigment flakes so as to provide images that can be utilized in security applications.
All of the aforementioned patents and applications are incorporated herein by reference, for all intents and purposes.
Although some pigment flakes suspended in a carrier vehicle can be aligned in electric fields, magnetically orientable flakes aligned in a magnetic field are generally more practicable. The term magnetic flakes used hereafter means flakes that can be aligned in a magnetic field. These flakes may or may not be magnetic themselves.
Optically variable devices are used in a wide variety of applications, both decorative and utilitarian, for example, such devices are used as security devices on commercial products. Optically variable devices can be made in numerous ways to achieve a variety of effects. Examples of optically variable devices include the holograms imprinted on credit cards and authentic software documentation, color-shifting images printed on banknotes, and enhancing the surface appearance of items such as motorcycle helmets and wheel covers.
Optically variable devices can be made as film or foil that is attached to an object, and can also be made using optically variable pigments. One type of optically variable pigment is commonly called a colour-shifting pigment because the apparent color of images appropriately printed with such pigments changes as the angle of view and/or illumination is tilted. A common example is the “20” printed with colour-shifting pigment in the lower right-hand corner of a U.S. twenty-dollar bill, which serves as an anti-counterfeiting device.
Some anti-counterfeiting devices are covert, while others are intended to be noticed. Unfortunately, some optically variable devices that are intended to be noticed are not widely known because the optically variable aspect of the device is not sufficiently dramatic. For example, the color shift of an image printed with color-shifting pigment might not be noticed under uniform fluorescent ceiling lights, but more noticeable in direct sunlight or under single-point illumination. This can make it easier for a counterfeiter to pass counterfeit notes without the optically variable feature because the recipient might not be aware of the optically variable feature, or because the counterfeit note might look substantially similar to the authentic note under certain conditions.
As need continues to design devices that are difficult to counterfeit and easy to authenticate, more interesting and useful devices become available.
For example, United States Patent application publication number 20060194040 in the name of Raksha et al. discloses a method and image formed by applying a first coating of magnetically alignable flakes; magnetically aligning the first coating of alignable flakes; curing the aligned flakes, and repeating the steps by applying a second coating of magnetically alignable flakes over the first cured aligned coating of flakes, aligning the second coating of flakes in a magnetic field and subsequently curing the second coating. This two-step coating, aligning and curing sequence allows first applied flakes to be magnetically aligned in a different orientation to the second applied flakes.
Although patent application 20060194040 provides a useful result, it would be desirous to achieve similar yet different images wherein fields within an image could be oriented differently, and wherein this two-step coating sequence was not required.
Furthermore, it would be useful to provide a method and resulting image wherein regions of an image formed by field aligning flakes could be utilized to form a mosaic wherein stamped-out aligned portions of an aligned image could be reoriented and applied to an object or substrate so as to form a desired pattern or image that differs from the originally aligned image.
It is an object of the present invention, to provide optically variable images wherein one or more regions of an image of field aligned flakes are stamped out, and are affixed to substrate in a preferred orientation.